Patent Eligibility Restoration Act of 2023 This bill amends the law relating to patent subject matter eligibility to establish that only specified subject matter (e.g., a natural process wholly independent of human activity) is ineligible for patenting. (Currently, subject matter eligibility is determined by examining whether the claimed invention is directed to certain ineligible categories, and if so, whether there is an inventive concept. Subject matter eligibility is one of several requirements that an invention must satisfy in order to receive patent protection.) Under this bill, an invention shall be considered to involve patent-ineligible subject matter only if it falls within specified categories, such as (1) a mathematical formula that is not part of a useful process, machine, manufacture, or composition; (2) a mental process that is performed solely in the human mind; or (3) an unmodified human gene as the gene exists in the human body.